A number of states provide for a manual recount of a small sample of the ballots cast as a way to detect voting system errors. In California, although there is a requirement for a one percent manual recount, there are no rules on how this should be carried out. If not done carefully, however, the recount will not accomplish the task assigned to it. In particular, it may fail to detect election fraud committed by hackers inside or outside of the elections department.
Valdis Krebs explores the behavior of voters, focusing on how social knowledge greatly affects voter choice. As he writes, "after controlling for personal attitudes and demographic membership, researchers found that the social networks, [which] voters are embedded in, exert powerful influences on their behavior." This is related with two other models of voter behavior. The first, the atomized model, has "the voting public [as] an aggregation of autonomous decision-makers, each making a decision based on personal rationale and/or emotion" while the second is the demographic voter, "here the voter is not viewed as isolated and autonomous, but as a member of a demographic group which can influence or predict the voter's choices."
Read the document here (pdf)